This application is related to Japanese Patent Application No. 2000-178648 filed on Jun. 14, 2000, whose priority is claimed under 35 USC xc2xa7119, the disclosure of which is incorporated by reference in its entirety.
1. Field of the Invention
The present invention relates to an information recording and reproducing device, more particularly, an information recording and reproducing device suitable for a laser-assisted magnetic recording and reproducing system which is a high-density recording and reproducing system, a tracking servo system therefor and a recording medium therefor.
2. Description of Related Art
In an optical disk device and a magneto-optical disk device, in general, a continuous servo system using a guide groove or a sample servo system using a wobble pit as disclosed by Japanese Unexamined Patent Publication No. HEI 1(1989)-128276 has been used as a tracking servo system for determining the position of a head with respect to the disk.
By the continuous servo system, positional information on the optical disk is obtained by detecting a change in the amount of light diffracted by the guide groove with use of reflection of a light beam.
By the sample servo system using the wobble pit, pits for tracking are formed at regular intervals in a track direction, and positional information on the optical disk is obtained by detecting a change in the amount of light diffracted by the wobble pit with use of reflection of a light beam applied onto the optical disk like the continuous servo system.
In a magnetic disc device, since the distance between a magnetic head and a disk surface is only several tens of nanometers, the disk surface is required to be extremely flat and smooth. Therefore, desirably the disk surface is as free of surface treatment such as guide grooves or wobble pits as possible, which are adopted in the optical disk and the magneto-optical disk. For this reason, a special servo pattern for detecting relative positions of the head and tracks on the disk is generally recorded beforehand as magnetic information on the disk surface (see Visual Information Media Journal, Vol.52, No.10, pp.1412-1415(1998)).
The machining of the disk surface to provide unevenness, which has been applied for realizing the tracking servo in the optical disk and the magneto-optical disk may cause a recording/reproducing accuracy to deteriorate because variation in the shape and reflectance of the guide groove affects an error signal. In order to increase a track density, the guide groove needs to be formed with improved accuracy. However, in this case, there is a problem that the formation of the guide groove takes more time and more costs.
In a laser-assisted magnetic recording and reproducing system, which uses a laser beam as a heat source, a magnetic head is used in addition to an optical head. Therefore, like the conventional magnetic recording and reproducing system, extreme flatness and smoothness are required. It is desirable that the disk surface be not machined to have guide grooves or the like.
Further, in the laser-assisted magnetic recording and reproducing system, since a spot diameter of the laser beam is smaller than the length of the magnetic head in a track width direction, the width of a recording bit to be formed is determined by the spot diameter of the laser beam. Therefore, the accuracy of tracking needs to be determined on the basis of a light beam diameter.
However, in the currently available laser-assisted magnetic recording and reproducing system, there is not a tracking servo system in which both light beam diameter and magnetic signals are considered, and a highly accurate servo control cannot be performed.
The present invention has been made to provide an information recording and reproducing device which enables a highly accurate control of track position by detection of optical and magnetic information, and a tracking servo system for the device.
The present invention provides an information recording and reproducing device comprising: a magnetic information detecting section for magnetically detecting magnetic information recorded at a given position on a recording medium; an optical information detecting section for optically detecting optical information recorded at a given position on each track of the recording medium; and a positional control section for controlling a position on the track using the detected magnetic information and optical information.
These and other objects of the present application will become more readily apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.